Groundglass

Ground glass refers to glass that has been mechanically reduced to small particles by crushing, grinding, or milling. It can be a fine powder or larger granules and comes from recycled cullet or new glass stock. In ceramics, ground glass is used as frit in glazes; in optics and photography, a roughened plate called a ground-glass screen serves as a focusing aid.

Composition and properties: The composition follows the original glass. Most commonly it is soda-lime glass, but borosilicate or lead glass variants differ in silica content and color. Particles are angular; frits are submillimeter to about 0.5 mm, larger granules up to a few millimeters. Glass is hard (Mohs about 5.5) and chemically inert, though finely ground silica can act as a reactive filler in cement or glaze systems.

Production: Scrap glass is crushed, milled, and sieved to target sizes. Cleaned cullet and color-sorted streams improve consistency; frit-grade glass may be melted with fluxes to form glaze particles.

Uses: As an abrasive medium for cleaning and finishing; as a filler and pozzolanic additive in cement and concrete to improve durability. In ceramics, frit-grade ground glass provides glaze and flux. In art, it is used in mosaics and terrazzo, and in glass casting. In optics, ground-glass screens diffuse light and serve as focusing aids in traditional cameras.

Safety and environment: Glass dust poses inhalation hazards; use dust control, PPE, and protective equipment. Recycle glass where possible; handle powders to prevent airborne dispersion. Disposal follows local waste regulations.